The set of projective projectively extended real numbers. Unfortunately, the notation is not standardized, so the
set of affinely extended real numbers,
denoted here 
,
is also denoted 
by some authors.
R^*
See also
Affinely Extended Real Numbers, Projectively Extended Real Numbers, R, R--, R-+Explore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "R^*." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/R-Star.html